The pipes concerned are plastics pipes now being introduced in preference to metal pipes, for reasons of corrosion resistance and relative ease of jointing, for the transportation of liquid or gaseous fluids, for example petrol or drinking water. However, plain plastics pipes can allow substances in the pipe material itself or from outside the pipes to percolate into and contaminate the fluids, or conversely allow the fluids to percolate to the outside and pollute the environment. To prevent any such percolation, plastics pipes are being provided with thin metallic liners, but these complicate their jointing together.